Born in Belcherville, Texas, Fitts received his law degree in 1916 from the University of Southern California and while a student there worked as a clerk for prominent attorney Earl Rogers.

Fitts was elected to a second term as district attorney in 1932, and investigated the death of Hollywood producer-director-screenwriter Paul Bern, husband of actress Jean Harlow.

Samuel Marx, in his book Deadly Illusions (1990), accused Fitts of having been bribed by Metro-Goldwyn-Mayer (MGM) studio executives to accept Bern's death as suicide, to avoid a scandal.

He has also been accused of using his position to block action against the rapist of Patricia Douglas at an MGM Sales Convention in 1937, a case that was the subject of David Stenn's 2007 documentary film Girl 27.

Fitts was indicted for bribery and perjury in 1934 for allegedly taking a bribe to drop a statutory rape charge against a millionaire real-estate promoter, but was acquitted two years later.

Fitts, John D. Fredericks (1903–1915), and Steve Cooley (2000-2012) are the only Los Angeles County district attorneys to serve three complete terms.